To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a “beyond 4G network” or a “post long term evolution (LTE) system.”
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like.
In the 5G system, hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
In order to provide wireless communication service to a user, a remote node generally performs random access to access a higher node (e.g., a host node). When the remote node attempts such random access, a signal for random access may not be transmitted to the host node due to a channel state or interference with another signal, or the host node may reject the attempt at random access. When the random access fails for this reason, the remote node repeatedly attempts the random access until the random access is successful. Such repetitive random access may cause excessive power consumption by the remote node that performs the random access and may cause interference with another remote node.
As terminals having various functions propagate increasingly, an amount of uplink data transmitted in a wireless environment increases. Also, the number of users demanding more rapid uplink data transmission grows fast.
In the LTE Advanced Pro and the emerging 5G cellular networks, Machine-to-Machine (M2M) communications and Internet of Things (IoT) will play important roles. M2M and IoT enable connections between new types of terminals such as body sensors, vehicles, smart meters and the like, alongside the more familiar mobile phones. The upcoming LTE standards and 5G systems commit not only to support a massive number of M2M/IoT nodes but also to provide low latency access for M2M/IoT. This poses certain problems when it comes to supporting such a large number of new network entities.
It is estimated that by the year 2020, the number of connected IoT entities will reach 50 billion, and these devices are expected to experience a low end to end (E2E) latency—approximately 10% of that experienced in 4G systems.
Such a large number of nodes introduce pressure on the scarce resources available for random access. When such a massive number of devices try to initiate random accesses to the network, they may collide with each other, resulting in large latencies, which are not generally acceptable.
The massive number of IoTs and M2M entities and transactions in a network introduces pressure on the scarce resource for random access. The current LTE standard procedure of random access consists of four steps. In step one, a User Equipment (UE) transmits a randomly selected preamble sequence on Physical Random Access Channel (PRACH) to a base station (BS). In step two, the BS transmits a Random Access Response (RAR) on the Physical Downlink Shared Channel (PDSCH) in response to the detected preamble sequence. In step three, the UE transmits its identity and other messages (e.g., scheduling request) to the BS using the Physical Uplink Shared Channel (PUSCH) resources assigned in the RAR in the second step. In the last step, the BS echoes the identity of the UE received in the third step on PDSCH.
However, when a massive number of nodes try to initiate random accesses, they may collide with each other, resulting in PRACH overload and large—and often unacceptable—connection latencies. Currently different strategies have been proposed to deal with massive random accesses in the medium access control (MAC) layer. However, these methods are typically not sufficient to meet the latency requirements as MAC layer signaling is not as responsive as physical layer signaling.
There is therefore a desire to provide an improved random access mechanism which avoids this and other problems experienced in the prior art.